The invention relates to a method and apparatus for inspecting the recording medium of a disk drive. More particularly, the invention relates to a method and apparatus for enhancing accuracy in a disk defect detection process.
The hard disk drive (HDD) is a data storage device adapted to the recording and reproduction of data using a magnetic head. The data storage capacity, device integration density and physical miniaturization of conventional HDDs have all increased during recent years. Data recording density in a direction of disk rotation may be expressed using a bits per inch (BPI) value. Data recording density in a radial direction across the disk may be expressed using a tracks per inch (TPI) value. However expressed, data recording density has increased dramatically in contemporary HDDs. As a result, ever finer and more delicate mechanisms are required to read data that has been recorded with greatly increased density on the most recent HDDs.
The “disk” recording medium used in a HDD will typically include normal and defective regions. Data written to some physically defective regions will be reproduced with signals having reduced amplitude and/or degraded signal to noise ratio, as compared with signals resulting from normal data reads. At some point, the coherency of the data signals resulting from data read operations to defective disk regions can not be ensured. Accordingly, a disk defect inspection must be performed during the process of manufacturing an HDD in order to ensure the performance quality of the HDD.